The tracing_set_trace_write() function just removes the trailing whitespace
from the user supplied tracer name, but the leading whitespace should also
be removed.

In addition, if the user supplied tracer name contains only a few
whitespace characters, the first one will not be removed using the current
method, which results it a single whitespace character left in the buf.

To fix all of these issues, we use strim() to correctly remove both the
leading and trailing whitespace.

Signed-off-by: Yuntao Wang <ytcoode@gmail.com>
---
 kernel/trace/trace.c | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index a569a0cb81ee..a6e77db764cf 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -6433,7 +6433,7 @@ tracing_set_trace_write(struct file *filp, const char __user *ubuf,
 {
 	struct trace_array *tr = filp->private_data;
 	char buf[MAX_TRACER_SIZE+1];
-	int i;
+	char *name;
 	size_t ret;
 	int err;
 
@@ -6447,11 +6447,9 @@ tracing_set_trace_write(struct file *filp, const char __user *ubuf,
 
 	buf[cnt] = 0;
 
-	/* strip ending whitespace. */
-	for (i = cnt - 1; i > 0 && isspace(buf[i]); i--)
-		buf[i] = 0;
+	name = strim(buf);
 
-	err = tracing_set_tracer(tr, buf);
+	err = tracing_set_tracer(tr, name);
 	if (err)
 		return err;
 
-- 
2.35.0.rc2

On Fri, 21 Jan 2022 09:56:23 +0000
Yuntao Wang <ytcoode@gmail.com> wrote:

> The tracing_set_trace_write() function just removes the trailing whitespace
> from the user supplied tracer name, but the leading whitespace should also
> be removed.
> 
> In addition, if the user supplied tracer name contains only a few
> whitespace characters, the first one will not be removed using the current
> method, which results it a single whitespace character left in the buf.
> 
> To fix all of these issues, we use strim() to correctly remove both the
> leading and trailing whitespace.
> 
> Signed-off-by: Yuntao Wang <ytcoode@gmail.com>

Added to my queue.

Thanks,

-- Steve